What can anyone say about New York City that has not already been expressed by Hart Crane, Elizabeth Bishop, Lorca, Whitman, Lou Reed, Langston Hughes, Martin Scorsese, Patti Smith, Kurtis Blow and a thousand other writers, musicians, filmmakers, painters and, yes, photographers? Like London, Paris, Rome and a handful of other great cities, Gotham seems to consciously challenge artists of every stripe to somehow convey even a sliver of the ceaseless, panoramic multiverse it contains—while confronting the poet, painter, filmmaker and photographer with a living tableau that, by its nature, defies definition.

And still . . . every day, in every medium, men and women address the world of New York, hoping to somehow witness and share something of its great spirit.

Does the New York that Whitman celebrated in Leaves of Grass (“The beautiful city, the city of hurried and sparkling waters! the city of spires and masts!. . . my city!”) bear any resemblance to the melancholic landscape Lou Reed evoked in “Perfect Day” or the intoxicating dystopia Scorsese and Schrader brought to life in Taxi Driver? Of course it does—in that these and countless other visions of New York have forged the complex, contradictory idea of the city that most of us carry around in our minds and our hearts.

For those of us who were in New York on Sept. 11, 2001, and for billions more who watched 9/11 unfold on TV and online, that 20th-century idea—of what the city meant to New Yorkers and to the rest of the world—will likely never hold sway again. It has been changed, changed utterly.

Moreover, for some who witnessed the 2001 attacks on New York—and on the Pentagon and the plane that went down in Pennsylvania—the scale of the carnage in Lower Manhattan transformed the entire city, in an instant, from a place they called home to a ruin they had to leave behind forever.

For countless others, the love we always had for New York only grew stronger after seeing it so savagely attacked. Our connection to the city, and to other New Yorkers, now had about it a sense of defiance coupled with a kind of rough tenderness: the metropolis that had always felt so huge and indomitable suddenly seemed painfully vulnerable and in need of protection. Our protection.

Here, LIFE.com pays tribute to New York—specifically, to the storied landscape of Lower Manhattan, where 400 years ago New York was born—in photographs made in the decades before the Twin Towers anchored the foot of the island. Wall Street, Battery Park, the Brooklyn Bridge, Trinity Church, the Statue of Liberty and the vast, shimmering harbor—they’re all here: landmarks that, despite everything, retain their place in the collective imagination, captured by some of the finest photographers of the 20th century.